Roller blinds are a popular form of window treatment which is useful in controlling the amount of light passing through the window. Roller blinds consist of a fabric blind wrapped around a roller tube which is mounted at the top of the window and usually contained within some sort of elongated roller tube housing having a decorative front fascia. A control mechanism is generally provided for raising and lowering the fabric blind by rotating the roller tube. A bottom bar is often mounted at a bottom end of the fabric blind in order to weigh down the end of the blind and to provide an aesthetically pleasing finish to the bottom edge of the blind.
One of the existing problems with many roller blind control mechanisms currently on the market is the likelihood that a user can raise the blind too much and cause the bottom bar to jam into the roller tube housing. In order to prevent this, it is possible to design the roller tube housing to narrow the space through which the blind passes in order to block the bottom bar from entering the housing. However, while potentially effective, a narrow opening for allowing the fabric to pass through makes the roller blind more complicated to install. An improved mechanism for stopping the upward moving of the bottom bar is therefore desirable.